[unreadable] The broad objective of this Bioengineering Research Grant is to study biomechanical interactions of angiogenic microvessels with the extracellular matrix (ECM) on the microscale level. We will answer the following questions: How does angiogenesis influence global and local ECM material properties and ultrastructure? Is local angiogenic sprouting correlated with the stress state as predicted by computational mechanical modeling, MMP expression and ECM ultrastructure? Does mechanical conditioning of vascularized constructs influence angiogenic sprouting? To answer these questions, we will develop and apply novel experimental and computational techniques to study a 3D in vitro angiogenesis model. In the first specific aim, we will develop techniques to simulate the microscale biomechanical behavior of vascularized collagen gels using the Material Point Method (MPM), using volumetric confocal images as the basis for generating the geometry of the computational domain. In Aim 2, methods will be developed to nondestructively measure collagen gel ultrastructure, microvessel geometry and emission spectra using spectrofluorimetry and multiphoton fluorescence microscopy. In Aims 3 and 4, these highly novel approaches will be combined with traditional approaches for experimental measurements of biomechanical behavior, gene expression and protein expression to examine the mechanisms that are responsible for alterations in ECM material properties during angiogenesis. Finally, we will examine the effects of mechanical conditioning on microvessel sprouting and growth. The proposed experiments will provide an information base on the magnitudes and frequencies of forces that most influence the angiogenic vessel. A better understanding of the relationship between angiogenic vessels, the surrounding ECM structure, and the mechanics of the tissue undergoing angiogenesis will provide the basis for improved control of tissue vascularization in both native tissues (e.g., repairing ischemic tissue) and tissue engineered constructs. [unreadable] [unreadable]